Fuel injected internal combustion engine

ABSTRACT

An internal combustion engine having a fuel injector (7) arranged for injecting fuel into a combustion chamber, the fuel injector (7) including a nozzle chamber (25) having a selectively openable nozzle (15) at one end to communicate the nozzle chamber (25) with the combustion chamber and including a fuel metering device (14) arranged to selectively deliver fuel to the nozzle chamber (25). There is also provided a gas chamber (10) adjacent the combustion chamber and in communication with the nozzle chamber (25). Preferrably, the gas chamber (10) is located within the cylinder head (1) adjacent the nozzle chamber (25).

This invention relates to a fuel injected internal combustion engine andin particular to a direct injected internal combustion engine, that is,an engine wherein individual metered quantities of fuel are injecteddirectly into the respective cylinder(s) of the engine. Moreparticularly, the invention is directed to such engines wherein the fuelis injected entrained in a gas, preferably air.

Engines of the above type are known and typically incorporate areservoir for the gas used in the injection process wherein the gas atan appropriate pressure is held and sequentially delivered to therespective injector(s) of the engine to carry out the injection process.In multi-cylinder engines of the above type, it has been suggested inprior patent applications to provide a plenum chamber in directcommunication with each of the injector units as the source ofcompressed gas.

It has been proposed to take compressed gas from the cylinders of theengine for subsequent use as a supply of high pressure gas for effectingthe injection of fuel into the engine combustion chambers. In two suchprior proposals, as disclosed in U.S. Pat. No. 2,710,600 and GB PatentApplication No. 2093113, coaxial fuel and air chambers are provided withthe fuel being delivered to the fuel chamber and gas from a combustionchamber to the gas chamber. The gas is further compressed in this gaschamber to effect transfer of the gas to the fuel chamber and subsequentdelivery of the fuel entrained in the gas to the combustion chamber. Amore complex system of extracting high pressure gas from the combustionchamber for use in subsequent injection of fuel is disclosed in theApplicant's U.S. Pat. No. 4,781,164. The proposals disclosed in this USpatent are relatively complex and in each instance supply the gasextracted from the combustion chamber to an external chamber orreservoir from which it is subsequently supplied to the air/fuelinjectors.

Further, there is disclosed in Japanese Patent Application Publication64-19170 an engine having individual systems for delivering fuel andcompressed air independently to the combustion chamber of an engine. Therespective locations of the air and fuel delivery points are arranged sothat the air and fuel are mixed on entry to the combustion chamber. Itis proposed that by injecting the air into the combustion chamberindependently of the injection of the fuel, the timing of thecommencement and conclusion of the delivery of the air can beindependently varied in relation to the delivery of the fuel. Theadvantage of this independent delivery of the fuel and air to thecombustion chamber is said to be that it provides unrestricted selectionof the timing and duration of the supply of air so that the mostbeneficial effect is achieved in relation to the management of thecombustion process.

It is the object of the present invention to provide an internalcombustion engine having a fuel injection system incorporating acompressed gas supply which is constructed and arranged to notsubstantially increase the external physical dimensions of the engineand which will contribute to the effective performance of the injectionsystem and consequently of the engine.

With this object in view, there is provided an internal combustionengine having at least one combustion chamber, and respective fuelinjector means arranged to deliver fuel to each said combustion chamber,each fuel injector means including a nozzle chamber having a selectivelyopenable nozzle operable to communicate the nozzle chamber with thecombustion chamber, fuel metering means to meter fuel for delivery fromthe nozzle chamber to the combustion chamber, and gas chamber meansarranged adjacent said combustion chamber laterally spaced from saidnozzle chamber and in communication therewith to supply gas to thenozzle chamber, whereby the fuel is delivered from the nozzle chamber tothe combustion chamber entrained in the gas.

Preferably, the gas chamber means and/or the nozzle chamber are locatedwithin a cylinder head of the engine, and when both are so located, thegas chamber means and the nozzle chamber are preferably located adjacentone another. Normally the gas chamber is in direct communication withthe nozzle chamber. Alternatively the gas chamber means may be elsewherelocated in the wall of the combustion chamber.

Conveniently, in the operation of the above engine, the fuel injectormeans is arranged whereby during each combustion cycle of operation, thenozzle is opened for a period of time after completion of the fueldelivery from the nozzle chamber to the combustion chamber. This permitsgas from the combustion chamber to pass through the nozzle chamber toraise the gas pressure in the gas chamber means to a level sufficient toeffect the fuel delivery during the next engine cycle. Preferably, thenozzle is held open for a period after and continuous with the injectionof the fuel into the combustion chamber to allow gas to pass into thenozzle chamber to effect said rise of the gas pressure in the gaschamber means.

Conveniently, in a multi-cylinder engine, a single gas chamber means canbe provided communicating with the nozzle chamber associated with thecombustion chamber of each cylinder. The single gas chamber means can bein the form of a series of individual intercommunicating gas chambermeans, conveniently one for each combustion chamber. In thisarrangement, it is not necessary for each injector nozzle associatedwith each combustion chamber to individually be maintained open aftercompletion of fuel delivery to a respective combustion chamber for anextended period to provide a gas supply to maintain the required gaspressure. The gas supplied from one or two combustion chambers can besufficient to provide the required quantity and pressure of gas to allof the individual gas chamber means of a multi-cylinder engine. Further,where only one or some combustion chambers are employed to supply thegas to the gas chamber means of a multi-cylinder engine, that duty maybe rotated between respective combustion chambers of the engine in aselected sequence. It should however be noted that although it isconvenient, red cost and energy saving, to supply the gas to all of thegas chamber means from one or more cylinders of an engine, the gas canas an alternative be supplied from an external source, including anengine driven compressor or independent source.

It has been found that the overall height or width of the engine,depending upon the disposition thereof, can be reduced by incorporatingthe gas chamber means into the cylinder head or wall of the combustionchamber adjacent the fuel injector means when compared with priorconstructions wherein the fuel injector means and the gas chamber meansare typically arranged in a back to back or axially aligned relationwith respect to the nozzle chamber. In addition, when the gas chambermeans of the present invention is located within the cylinder head orotherwise close to the combustion chamber, any gas therein is generallyat a higher temperature than it would be in prior constructions.

The higher temperature of the gas can be of assistance in the control ofdeposits in the gas chamber means and nozzle chamber, and in thestability of operation of the engine, particularly during engine idleoperation. The improved stability at idle is believed to arise from"fuel hang-up" in the fuel injector means and/or the gas chamber meansbeing reduced as a result of the higher temperature of the gas in thenozzle chamber and the gas chamber means and the consequential increasedvaporisation of the fuel. Also, the proposed construction enables thegas path from the gas chamber means to the nozzle chamber, to be reducedin length.

The invention will now be described in more detail with reference to theaccompanying drawings of two practical arrangements of an enginecylinder head incorporating the fuel injector means and gas chambermeans as proposed herein.

In the drawings,

FIG. 1 is a cross-sectional view of a cylinder head incorporating a fuelinjector means and gas chamber means; and

FIG. 2 is a similar cross-sectional view of an alternative constructiontherefor.

Referring now to FIG. 1, the engine cylinder head 1 is suitable for aconventional two stroke cycle engine. Further, the cross-section asshown can be considered as representing a single cylinder of amulti-cylinder engine or a single cylinder engine.

A conventional spark plug 5 is removably screwed into a suitably locatedthread passage 6 to project into a combustion chamber 3. A two fluidfuel injector 7 of known construction is located in a bore 8 in thecylinder head 1 to project into the combustion chamber 3 in a knownmanner. A gas chamber 10 is partly formed by a cavity 9 formed withinthe cylinder head 1 and partly in a detachable cover plate 11. The gaschamber 10 is in continuous communication with the fuel injector 7 byway of a passage 12.

The fuel injector 7 includes a nozzle 15 received in the bore 8 in thecylinder head 1 and a popper valve 16 controlled by a solenoid unit 18having an armature 21 attached to a stem 22 of the valve 16. Thesolenoid 18 is cyclically energised in the known manner to open andclose the valve 16 for the delivery of fuel entrained in air to thecombustion chamber 3. A fuel metering unit 14 cyclically deliversmetered quantities of fuel into an axial passage 23 within the stem 22which passes via lateral passages 24 in the stem 22 into an annularcavity 25 surrounding a lower end of the valve 16 which is in directcommunication with an upstream side of a valve head 27 of the valve 16.Further information in regard to the fuel injector 7 is not provided asit is a well known construction, one example being disclosed in theApplicant's U.S. Pat. No. 4,934,329.

The nozzle 15 of the fuel injector 7, has a laterally disposed aperture26 located to provide communication between the passage 12 and theannular cavity 25 about the exterior of the lower end of the valve 16.It is thus seen that there is a continuous free communication betweenthe gas chamber in the cylinder head 1 and the annular cavity 25 in thefuel injector 7.

In the operation of an engine using the arrangement as above described,it is to be understood that the delivery of a metered quantity of fuelfrom the metering unit 14 into the axial passage 23 within the valvestem 22, is a separate operation from the opening of the valve 16 forthe delivery of fuel entrained in a charge of gas from the gas chamber10 through the nozzle 15 to the engine combustion chamber 3. Assuming astarting position wherein the gas chamber 10 is charged with gaspreviously received from the engine combustion chamber 3 and a piston(not shown) of an associated cylinder (not shown) corresponding with thecombustion chamber 3 is moving upwardly on a compression stroke of theengine, and a metered quantity of fuel has been delivered by themetering unit 14 into the axial passage 23 within the valve stem 22 ofthe fuel injector 7, then upon opening of the valve 16 at a point in thecompression stroke when the cylinder pressure is substantially below thepressure of the gas in the gas chamber 10, the metered quantity of fuelwill be discharged through the nozzle 15 into the combustion chamber 3entrained in gas which will flow from the gas chamber 10 through thepassages 12 and 26 into the fuel injector 7 and hence, through theannular cavity 25 and out through the open nozzle 15.

After a relatively short interval of time, all of the metered quantityof fuel will have been discharged through the nozzle 15 into thecombustion chamber 3, and the continuing upward movement of the pistonin the cylinder will provide a resultant rising pressure in thecombustion chamber 3. At this point in time, the nozzle 15 is stillmaintained open to facilitate the subsequent re-pressurisation of thegas chamber 10. In this regard, a condition will be reached where thepressure in the combustion chamber 3 is greater than that in the gaschamber 10 and there will be a reverse flow of gas from the combustionchamber 3, through the open nozzle 15 and passages 26 and 12, into thegas chamber 10 to replace the gas discharged during the previousdelivery of the fuel, and to also raise the pressure of the gas in thegas chamber 10 to a level substantially above the pressure in thecombustion chamber 3 at the time of initial opening of the nozzle 15, toeffect subsequent delivery of the fuel to the combustion chamber 3. Thenozzle 15 is then closed to retain the gas in the gas chamber 10 whichis then in condition to effect delivery of fuel to the combustionchamber 3 during the next engine cycle.

In the construction shown in FIG. 1, the cover plate 11 provides accessto the interior of the cavity 9 for machining or other finishingtreatment of the internal surface of the cavity 9. The cover plate 11may also be used in a modified form to provide communication between thegas chambers 10 of two or more cylinders of a multi-cylinder enginewhere gas is supplied from any number of the engine cylinders or from anexternal source. The cover plate 11 may also enable communicationbetween the individual gas chambers 10 of a multi-cylinder engine with asingle plenum chamber wherein the source of pressurised gas thereof maybe the engine combustion chamber(s), an engine driven compressor, or anexternal source. The variations can be used where the cavity 9 is formedin the cylinder head or the cylinder wall.

Also, the shape of the cavity 9 as shown in FIG. 1 which tapers towardsthe passage 12 promotes the flow of any fuel which may enter the gaschamber 10 towards the passage 12 when the axis of the gas chamber 10 isvertical and the passage 12 lower than the gas chamber 10. Further, thegenerally hemispherical shape of the remainder of the cavity 9 providesa minimum surface area to volume ratio and hence contributes to reducedfuel hang-up.

FIG. 2 shows a modified version of the fuel injection system as shown inFIG. 1 wherein the principal differences reside in the location of thefuel metering device that delivers the metered quantity of fuel to theannular cavity 25 and the consequential alterations to the constructionof the two fluid fuel injector 7.

In the embodiment shown in FIG. 2, the fuel is delivered by the meteringdevice 32 through the fuel line 30A and needle 30B into the throat ofthe passage 12 and hence through the aperture 26 and hence into theannular cavity 25 about the exterior of the lower end of the valve 16.It will be appreciated that when the valve head 27 is in the openposition gas will flow from the chamber 10 through the passages 12 and26 to thereby entrain the fuel therein and in the annular cavity 25 todeliver same through the open injector nozzle 15. The length anddirection of the needle 30B can be varied or adjustable to achieve thebest operational position thereof relative to the gas chamber 10 and thepassage 12. Also, the needle 30B can extend through the passages 12 and26 to deliver the fuel directly into the annular cavity 25. Further, theneedle 30B can extend into the cavity 25 and can be configured at theend thereof so as to direct fuel towards the valve head 27.

It will be noted that although the external configuration of the upperportion of the valve stem 22 is the same as in FIG. 1, the passage 23through the stem is omitted to provide a solid stem as seen FIG. 2. Inthis embodiment, the fuel does not pass down through the center of thestem 22 but is delivered directly into the cavity 25 through theaperture 26 via the needle 30B.

This construction as shown in FIG. 2 reduces the length of the flow pathof the fuel from the metering location to the injector nozzle 15 andhence reduces fuel hang-up and the adverse effect thereof on the controlof the actual quantity of fuel delivered. The length of the flow path ofgas from the gas chamber 10 is also reduced, and the solenoid unit 18has reduced exposure to the hot gases entering the fuel injector 7resulting in the operating temperature of the solenoid unit 18 beinglower than would arise in prior known constructions such as thoseinvolving a "piggy-back" or axially aligned arrangement of the gaschamber and fuel injector as hereinbefore described. The resistance ofthe coil of the solenoid unit 18 increases with increase in temperaturewhich is of course undesirable as it increases the current draw of thesolenoid unit 18.

Although not shown in FIG. 1 or FIG. 2, appropriate guide projectionsmay be provided on the external surface of the lower portion of thepopper valve 16 which slidably engage the adjacent inner concentricsurface of the nozzle 15 to thereby assist in maintaining the valve head27 concentric with the valve seat of the nozzle 15. This construction iswell known and commonly used in a wide range of known injectorconstructions, one example being disclosed in the Applicant's U.S. Pat.No. 4,759,335.

The fuel may be provided to the needle 30B by any known fuel meteringdevice, but preferably a device insensitive to pressure such as apositive displacement pump, and one form of fuel metering deviceparticularly suitable for use in this environment is that disclosed inthe applicants prior copending International Patent Application No.PCT/AU92/00561, or International Patent Application No. WO 93/00502.

The above described constructions wherein the gas chamber 10 isincorporated in the cylinder head 1, avoid the necessity of providing anindependent source of compressed gas for delivering fuel to the enginesuch as a compressor, thereby substantially reducing the overallmanufacturing costs of the fuel injection system. Further, it has beenfound that the reverse flow of high temperature gases from thecombustion chamber 3 through the nozzle 15 of the fuel injector 7 intothe gas chamber 10 has the effect of maintaining the insides of thenozzle 15 and the gas chamber 10 substantially free of deposits ofpartially combusted fuel and consequently leads to a more efficientoperation of the fuel injector 7 over extended periods. The hightemperature in the gas chamber 10 assists in the vapourisation of thefuel and reduces fuel hang-up on the inner surfaces of the nozzle 15 andthe surfaces of the valve 16.

The incorporation of the gas chamber 10 adjacent the combustion chamber3, such as in the cylinder head 1 or wall of the combustion chamber 3,also reduces the overall physical size of the injector system. Further,as a result of the high temperature in the walls of the gas chamber 10,the build-up of deposits on the internal surfaces of the gas chamber 10and in the nozzle 15 are typically reduced.

Even if the high pressure gas is supplied to the gas chamber 10 by acompressor, in preference to the combustion chamber 3, the aboveadvantages are still achieved as a result of the high temperature in thewalls of the gas chamber 10.

Further, it is to be understood that although the cylinder head 1illustrated in the drawing is for a two stroke cycle engine, theinvention is equally applicable to an engine operating on the fourStroke cycle. Also, it is to be understood that the gas can be air orany other gas and may contribute and assist in the overall combustionprocess as air does. Also, the fuel may be in a liquid vapour or gaseousform.

We claim:
 1. An internal combustion engine having at least onecombustion chamber, respective fuel injector means arranged to deliverfuel to each said combustion chamber, each fuel injector means includinga nozzle chamber having a selectively openable nozzle operable tocommunicate the nozzle chamber with the combustion chamber, fuelmetering means to meter fuel for delivery from the nozzle chamber to thecombustion chamber, and gas chamber means arranged adjacent saidcombustion chamber laterally spaced from said nozzle chamber and incommunication therewith to supply gas to the nozzle chamber, whereby thefuel is delivered from the nozzle chamber to the combustion chamberentrained in the gas.
 2. An internal combustion engine as claimed inclaim 1 wherein said fuel injector means is mounted in a wall of thecombustion chamber with the nozzle arranged to inject fuel directly intosaid combustion chamber.
 3. An internal combustion engine as claimed inclaim 1 or 2 wherein said gas chamber means is located in a wall of thecombustion chamber.
 4. An internal combustion engine as claimed in claim1 or 2 wherein said gas chamber means is located in an engine cylinderhead defining part of the combustion chamber.
 5. An internal combustionengine as claimed in claim 1 wherein the nozzle chamber is located in anengine cylinder head defining part of the combustion chamber.
 6. Aninternal combustion engine as claimed in claim 1 wherein the gas chambermeans is in continuous communication with the nozzle chamber.
 7. Aninternal combustion engine as claimed in claim 1 wherein the fuelinjector means is adapted to maintain the nozzle thereof open for aselected period between successive deliveries of fuel to the combustionchamber to permit gas to pass into the gas chamber means from thecombustion chamber through the nozzle and the nozzle chamber tore-establish a pressure in the gas chamber means above a preselectedlevel.
 8. An internal combustion engine as claimed in claim 7 whereinsaid fuel injector means is adapted to maintain the nozzle chamber incommunication with the combustion chamber for a period which allowssufficient accumulation of gas in the chamber means to effect successivedelivery of the fuel to the combustion chamber and the passage of gasinto the nozzle chamber.
 9. An internal combustion engine as claimed inclaim 1 wherein a fuel metering means is arranged to deliver fuel to ordirectly into the nozzle chamber through a duct.
 10. An internalcombustion engine as claimed in claim 9 wherein the duct extends throughthe gas chamber means.
 11. An internal combustion engine as claimed inclaim 1 wherein the fuel metering means is arranged to deliver the fuelinto the gas chamber means.
 12. An internal combustion engine as claimedin claim 1 wherein the fuel metering means is arranged to deliver thefuel into a passage communicating the gas chamber means with the nozzlechamber.
 13. An internal combustion engine claimed in claim 1 whereinthe fuel injector means includes a valve stem, and wherein the fuelmetering means is arranged to deliver fuel to the nozzle chamber througha passage extending longitudinally through the valve stem.
 14. Aninternal combustion engine as claimed in claim 1 being a multi-cylinderengine, each cylinder having a respective combustion chamber, fuelinjector means and gas chamber means, said gas chamber means of two ormore cylinders being in communication for the free passage of gastherebetween.
 15. An internal combustion engine as claimed in claim 14wherein the fuel injector means of at least one of those cylinders thathave the gas chamber means thereof in communication is adapted tomaintain the nozzle thereof open for a selected period betweensuccessive deliveries of fuel to the combustion chamber of the cylinderto permit gas to pass into the gas chamber means thereof from thecombustion chamber through the nozzle into the nozzle chamber and gaschamber to re-establish a pressure in each of the communicating gaschamber means above a preselected level.
 16. An internal combustionengine according to claim 1 claims wherein the gas chamber meansincludes a tapered portion tapering towards the nozzle chamber.
 17. Aninternal combustion engine according to claim 1 wherein the gas chambermeans includes a hemispherical portion facing the nozzle chamber.